This invention relates to a process for the preparation of fiberboards suitable for use as interior or exterior construction materials, furniture materials, interior materials for automobiles, cabinet materials for electric instruments and so on.
Fiberboards such as insulation boards are generally produced by either a wet shaping method or a dry shaping method. The wet shaping method includes the steps of dispersing defibrated cellulose fibers or pulp in water; homogeneously mixing a sizing agent such as a rosin, asphalt, paraffin, phenol resin, amino resin or starch to allow same to be adsorbed by the fibers or pulp; forming the dispersion into a wet mat of a desired thickness; dewatering the wet mat; and consolidating the dried mat under heat and pressure. In the dry shaping method, cellulose fibers are homogeneously mixed with a binder such as a phenol resin or amino resin, and the mixture is formed into a mat of a predetermined thickness, followed by a consolidation treatment by a hot press. Thus, the conventional method, irrespective of whether it is a dry method or a wet method, requires a step of commingling fibers with a sizing agent or a binder. Incidentally, the bending strength of fiberboards produced by the above known method depends upon its density. That is, in order for a fiberboard to have a high bending strength, it is necessary to increase the density of the board.